2019.4.32

2019.4.32

class Counter extends RecursiveTask<Integer>{
            public static final int THRESHOLD = 1000;
            private double[] values;
            private int from;
            private int to;
            private DoublePredicate filter;

            public Counter(double[] values, int from, int to, DoublePredicate filter){
                this.values = values;
                this.from = from;
                this.to = to;
                this.filter = filter;
            }

            protected Integer compute(){
                if(to - from < THRESHOLD){
                    int count = 0;
                    for(int i=from; i<to;i++){
                        if(filter.test(values[i]))
                            count++;
                    }
                    return count;
                }
                else{
                    int mid = (from + to) / 2;
                    var first = new Counter(values, from, mid, filter);
                    var second = new Counter(values, mid, to, filter);
                    invokeAll(first, second);
                    return first.join() + second.join();
                }
            }
        }